Alcohol Consumption and Risk of Thyroid Cancer: A Population Based Case-Control Study in Connecticut

Background: Studies examining the association between alcohol consumption and thyroid cancer risk have been inconsistent, in part due to varying types and amounts of alcohol consumption, incomplete information on confounders, and variations in genetic susceptibility in study populations. Methods: The present study analyzed data from a population-based case-control study in Connecticut in 2010-2011 including 462 histologically confirmed incident thyroid cancer cases and 498 population-based controls. Unconditional logistic regression was used to estimate associations between alcohol consumption and risk of thyroid cancer. Potential confounding variables were age, gender, race, education, body mass index, family history of cancer among first-degree relatives, history of benign thyroid disease, smoking status, and physical activity. Results: Ever consumption of alcohol was associated with a reduced risk of thyroid cancer (OR = 0.71, 95% CI: 0.54-0.95). The younger age at initiation and increasing duration of alcohol consumption were also associated with a reduced risk of thyroid cancer in a dose-dependent manner (P for trend = 0.041 and 0.0065, respectively). Compared to people who never drank alcohol, people who drank alcohol for >31 years were 50% less likely to develop thyroid cancer (OR = 0.50, 95% CI: 0.32-0.80). Alcohol consumption was associated with a reduced risk of papillary thyroid cancer (OR = 0.66, 95% CI: 0.49-0.88) and thyroid cancer with lager tumor size (>1 cm), but no significant association was found between alcohol consumption and non-papillary thyroid cancer or thyroid microcarcinoma. Analyses stratified by specific subtypes of alcohol demonstrated an inverse association for beer (OR = 0.69, 95% CI: 0.49-0.96) and wine consumption (OR = 0.71, 95% CI: 0.53-0.96) as compared to participants who never consumed alcohol, but no significant association was found for liquor consumption (OR = 0.75, 95% CI: 0.53-1.04). Conclusions: The study findings suggest an inverse association between alcohol consumption and risk of thyroid cancer. Future mechanistic study is warranted to elucidate the underlying mechanisms.